1. Field of the Invention
This invention relates to methods of and apparatus for positioning pallets, and more particularly to a method of and apparatus for positioning a pallet whereby the pallet disposed upon the roller chains of a horizontally disposed free flow conveyor is able to be stopped at a required position with a high degree of accuracy.
2. Description of the Prior Art
In a production or an assembly line of electrical parts, conventionally, the free flow conveyor has favorably been put into practical use. This horizontally disposed free flow conveyor mounted upon a conveyor frame consists of a large number of pallets which are freely loaded on endlessly circulating roller chains, and feeds in order a printed circuit board for electrical parts held on a pallet toward a work station, where every pallet is securely stopped at a required position before automatic insertion of electrical parts with the aid of an inserter or other similar devices is generally performed.
The prior art free flow conveyors, however, have demonstrated substantially great technical difficulties in their positioning operations to securely stop the pallet at the required position. And to minimize this difficulty various devices or systems have been brought forward. For example, a device for positioning a pallet in x- and y-directions, as shown in FIG. 1, was proposed to fit a wedge-shaped stopper 14 into a triangular notch 12 cut away on one side edge of a pallet 10. But this device contained disadvantages in requiring intricate mechanisms as well as installation costs because another arrangement was required to control the height in the z-direction. Such being the case with the conventional pallet positioning device, as a result of incorporating an independently driving mechanism requisite for x-, y-, and z-dirctions respectively, the positioning operation must be performed with a two-step action cycle, and thus another disadvantage existed in taking much time for positioning the pallet.